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B16.47 Series A vs Series B: What’s The Difference?

B16.47 Series A Series B Flanges

ASME B16.5 and ASME B16.47

ASME B16.5 standard covers steel pipe flanges and flanged fittings from NPS ½” through NPS 24” in pressure classes 150 to 2500. This includes pressure ratings, dimensions, tolerances, materials, marking, and testing.  ASME B16.5 and ANSI B16.5 only cover sizes up to 24 inches. For bigger sizes, ASME B16.47 standard covers pipe flanges in sizes 26” through 60” and in pressure class ratings 75, 150, 300, 400, 600, and 900. Then, ASME B16.47 is further divided into ASME B16.47 Series A and ASME B16.47 Series B flanges for Blinds and Weldnecks.

The designation formerly referred to as MSS SP-44 flanges are now considered ASME B16.47 Series A flanges, while API 605 flanges are now ASME B16.47 Series B flanges. Materials covered in this standard are the same as ASME B16.5 except for nickel alloys. Due to this, they share the same pressure-temperature chart for the selection of flange materials.

What is the difference between ASME B16.47 Series A and Series B flanges?

ASME B16 47 Series A flanges are thicker, heavier, and stronger than their Series B counterparts. They also can often handle more external loading than Series B. Series A flanges tend to be more costly than Series B flanges.

ASME B16.47 Series B flanges need more but smaller fasteners, such as bolts & nuts. They also usually have a smaller bolt circle diameter than Series A flanges. Generally, there is less flange movement after installation due to the smaller bolt circle diameter.

Both Series A and B define weld neck flanges and blind flanges in raised face type. However, Series A defines ring-type joint (RTJ) flanges from Class 300 through Class 900 within this standard while Series B does not.

Series A flanges are popular for new pipeline projects or equipment. Meanwhile, many choose Series B flanges for refurbishment or replacement jobs.

If you still need help deciding which is better for your project, pipeline, or job, feel free to call (281-484-8325) or  e-mail the Texas Flange sales office anytime from 8 a.m. to 5 p.m. Monday through Friday. Or you can drop a quick question or inquiry into our quick contact form. With our decades of expertise, we can help you get the flanges you need.

If you’d like to learn more about flange specifications, types, uses and more feel free to peruse our informational blog posts, free 3-D and CAD drawings, or flange charts.

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4 years ago

Great content! Super high-quality! Keep it up! 🙂

Rick Lim
Rick Lim
4 years ago

what is the 30 inch flat face flange flatness allowable tolerance? for oil storage tank manhole ?
API650 neither mention nor B616.47?

4 years ago
Reply to  Rick Lim

Flatness is not a tolerance listed in B16.47, but thickness is, so you can you run the trigonometry to determine a flatness for that particular size if the flange was wedge shaped with one side measuring at the high end of thickness tolerance and the opposite at the low end. We don’t normally see this being an issue since lathes are excellent at keeping a part flat. We also will usually regret super thin parts for this reason.

Feel free to email us or give us a call if you need any more assistance!

[email protected]

Diane Blackburn
Diane Blackburn
3 years ago

Thank you for the info. Very helpful.

M.Sivarama Krishnan
M.Sivarama Krishnan
2 months ago

In ASME B 16.47, Two types of flanges only available ? Such as blind and weld neck flange.